MINNEAPOLIS - A University of Minnesota sleep expert says the state health department may have jumped the gun by approving medical marijuana for sleep apnea.

The condition affects 18 million American adults, mostly males, according to the National Sleep Foundation. It causes the upper airway to collapse during sleep, which repeatedly interrupts breathing and can lead to serious health problems.

The latest research, funded by the National Institutes of Health, shows that synthetic THC, the main drug in marijuana, can stimulate the vagus nerve in the brain during sleep causing breathing to stabilize.

“It showed some pretty significant and impressive benefits for the two arms of the study that were not the placebo arm,” said Tom Arneson, research manager for the state health department Office of Medical Cannabis.

Based on this research, the health department commissioner, Dr. Ed Ehlinger, added sleep apnea to the approved conditions for medical marijuana use on Thursday.

But Dr. Michael Howell, a sleep expert at the University of Minnesota Department of Neurology, says there is too little research for him to recommend the drug to a patient.

“Based on the evidence we have right now, that’s premature,” said Howell.

Howell said the study is strong and the largest of its kind to date, but he would need further research to recommend the drug for sleep apnea.

In a press release Thursday, Ehlinger said, “Any policy decisions about cannabis are difficult due to the relative lack of published scientific evidence. However, there is increasing evidence for potential benefits of medical cannabis for those with severe autism and obstructive sleep apnea.”

While Howell is not yet convinced of the drug’s efficacy on sleep apnea, he believes the state’s decision will make it easier for researchers to find people to conduct further, more refined research on sleep apnea and the benefits of medical marijuana.